1. Field of the Invention
The present invention relates to a video encoding method and apparatus, and a video decoding method and apparatus, and more particularly, to a video encoding method and apparatus, and a video decoding method and apparatus, which are capable of improving efficiency of encoding a luminance component video signal by predicting information on various encoding modes of the luminance component video signal by using a result obtained by encoding a chrominance component video signal.
2. Description of the Related Art
In general, an initial video has an RGB color format when video images are captured. A video having the RGB color format is generally encoded into a video having a YUV (or YCbCr) color format. Here, a Y component indicates luminance data including brightness information, and U (or Cb) and V (or Cr) components indicate chrominance data including color information. In the RGB video, information is uniformly distributed over R, G, and B. In the YUV (or YCbCr) video, information is concentrated on the Y component, and the amount of information on the U (or Cb) and V (or Cr) components is reduced. This is advantageous in that a compression rate is increased when compressing a YUV video. In order to additionally improve the compression rate, in general, a YUV (or YCbCr) 4:2:0 video is used by sampling chrominance components U (or Cb) and V (or Cr) of the YUV (or YCbCr) video with a ¼ size of the luminance component.
When the YUV (or YCbCr) video is compressed, in general, the Y component is encoded independently of the U (or Cb) and V (or Cr) components. For example, in the MPEG-4 AVC/H.264 standard of the Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG (“Text of ISO/IEC FDIS 14496-10: Information Technology—Coding of audio-visual objects—Part 10: Advanced Video Coding”, ISO/IEC JTC 1/SC 29/WG 11, N5555, March, 2003) (hereinafter, referred to as MPEG-4 AVC/H.264), when the Y component is intra-video encoded, a spatial prediction process is performed by using nine prediction methods in units of 4×4 blocks along a prediction direction. In addition, the spatial prediction process is performed by using four prediction methods in units of 16×16 blocks along the prediction direction. However, since U (or Cb) and V (or Cr) component video signals are relatively simple compared with a Y component video signal, the spatial prediction process is performed with respect to the U and V component video signals by using four prediction methods in units of 8×8 blocks along the prediction direction independently of the Y component video.
When the Y component video signal is inter-video encoded, a motion is accurately compensated for, by expanding a predicted video signal by using a 6-tap filter. On the contrary, when the U (or Cb) and V (or Cr) component video signals are inter-video encoded, a motion is compensated for by using a bilinear filter. In a conventional method, the Y component video signal and the U (or Cb) and V (or Cr) component video signals are compressed by using independent methods.